Wireless signal transmission and reception method and device in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and, particularly, to a method and a device therefor, the method comprising the steps of: configuring a cell group including multiple Ucells; identifying subframe configuration information on a particular cell within the cell group; and configuring subframe transmission directions of cells within the cell group so as to be the same at the same time point, on the basis of the subframe configuration information on the particular cell, wherein the particular cell is one Ucell among the multiple Ucells within the cell group when the cell group includes only Ucells, and the particular cell is an Lcell when the cell group includes the Lcell.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for transmitting control information in awireless communication system and an apparatus for the same.

BACKGROUND ART

Generally, a wireless communication system is developing to diverselycover a wide range to provide such a communication service as an audiocommunication service, a data communication service and the like. Thewireless communication is a sort of a multiple access system capable ofsupporting communications with multiple users by sharing availablesystem resources (e.g., bandwidth, transmit power, etc.). For example,the multiple access system may include one of CDMA (code divisionmultiple access) system, FDMA (frequency division multiple access)system, TDMA (time division multiple access) system, OFDMA (orthogonalfrequency division multiple access) system, SC-FDMA (single carrierfrequency division multiple access) system and the like.

DETAILED DESCRIPTION OF THE INVENTION Technical Problems

An object of the present invention is to provide a method of efficientlyperforming a wireless signal transmission/reception process and anapparatus therefor. Another object of the present invention is toprovide a carrier aggregation method of effectively securing anavailable resource duration and an apparatus therefor.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solutions

According to an aspect of the present invention, provided herein is amethod of performing communication by a user equipment (UE) in awireless communication system, including configuring a cell groupincluding a plurality of unlicensed band cells (UCells); identifyingsubframe configuration information about a specific cell in the cellgroup; and configuring subframe transmission directions of cells in thecell group to be the same at the same timing, based on the subframeconfiguration information about the specific cell, wherein, if the cellgroup includes only the UCells, the specific cell is any one of theUCells in the cell group, and if the cell group includes a licensed bandcell (LCell), the specific cell is the LCell.

In another aspect of the present invention, provided herein is a userequipment (UE) for performing communication in a wireless communicationsystem, including a radio frequency (RF) module; and a processor,wherein the processor is configured to configure a cell group includinga plurality of unlicensed band cells (UCells), identify subframeconfiguration information about a specific cell in the cell group, andconfigure subframe transmission directions of cells in the cell group tobe the same at the same timing, based on the subframe configurationinformation about the specific cell, and wherein, if the cell groupincludes only the UCells, the specific cell is any one of the UCells inthe cell group, and if the cell group includes a licensed band cell(LCell), the specific cell is the LCell.

Configuring subframe transmission directions of cells in the cell groupto be same at the same timing may include configuring reserved resourceperiods (RRPs) on the UCells in the cell group to be the same and eachof the RRPs may indicate a resource temporarily configured on eachUCell.

The RRP may include a plurality of contiguous downlink (DL) subframesand a plurality of contiguous uplink (UL) subframes subsequent to the DLsubframes.

The RRP may include K1 contiguous DL subframes and K1 or fewercontiguous UL subframes subsequent to the K1 contiguous DL subframes.

If signal transmission is scheduled in an (n+1)-th subframe in the RRP,a signal transmission process may be performed according to a carriersensing result in an n-th subframe, wherein, if a signal related to aparameter indicated by a base station (BS) is detected in the n-thsubframe, signal transmission may be performed in the (n+1)-th subframe,and if no signal related to the parameter indicated by the eNB isdetected in the n-th subframe, whether signal transmission is performedin the (n+1)-th subframe may be determined according to an energy levelin the n-th subframe.

The wireless communication system may be a 3rd generation partnershipproject (3GPP) wireless communication system.

Advantageous Effects

According to the present invention, wireless signaltransmission/reception can be efficiently performed in a wirelesscommunication system. In addition, an available resource duration can beeffectively secured through a carrier aggregation method and anapparatus therefor.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

FIG. 2 illustrates a radio frame structure.

FIG. 3 illustrates a resource grid of a downlink slot.

FIG. 4 illustrates a downlink subframe structure.

FIG. 5 illustrates an example of Enhanced Physical Downlink ControlChannel (EPDCCH).

FIG. 6 illustrates the structure of an uplink subframe.

FIG. 7 illustrates a carrier aggregation (CA)-based wirelesscommunication system.

FIG. 8 illustrates a cross-carrier scheduling.

FIG. 9 illustrates carrier aggregation of a licensed band and anunlicensed band.

FIGS. 10 and 11 illustrate a resource reservation method on anunlicensed band.

FIG. 12 illustrates a communication procedure according to an embodimentof the present invention.

FIG. 13 illustrates a base station and a user equipment applicable to anembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE. While the following description is given,centering on 3GPP LTE/LTE-A for clarity, this is purely exemplary andthus should not be construed as limiting the present invention.

In a wireless communication system, a user equipment (UE) receivesinformation through downlink (DL) from a base station (BS) and transmitsinformation to the BS through uplink (UL). The information transmittedand received by the BS and the UE includes data and various controlinformation and includes various physical channels according totype/usage of the information transmitted and received by the UE and theBS.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the mean time, theUE may check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Downlink- to-Uplink Uplink- Switch downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3, a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present invention is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A basic resource unit of the data regionis an RB. Examples of downlink control channels used in LTE include aphysical control format indicator channel (PCFICH), a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of asubframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. The PHICHis a response of uplink transmission and carries an HARQ acknowledgment(ACK)/negative-acknowledgment (NACK) signal. Control informationtransmitted through the PDCCH is referred to as downlink controlinformation (DCI). The DCI includes uplink or downlink schedulinginformation or an uplink transmit power control command for an arbitraryUE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. A arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 PDCCH Number of Number of Number of format CCEs (n) REGs PDCCHbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number of Number of candidates candidates PDCCH Number of incommon in dedicated format CCEs (n) search space search space 0 1 — 6 12 — 6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission Mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (ports) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI Format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

FIG. 5 illustrates an EPDCCH. The EPDCCH is a channel additionallyintroduced in LTE-A.

Referring to FIG. 5, a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE may be allocated to a control region (see FIG.4) of a subframe. In the figure, the L-PDCCH region means a region towhich a legacy PDCCH may be allocated. Meanwhile, a PDCCH may be furtherallocated to the data region (e.g., a resource region for a PDSCH). APDCCH allocated to the data region is referred to as an E-PDCCH. Asshown, control channel resources may be further acquired via the E-PDCCHto mitigate a scheduling restriction due to restricted control channelresources of the L-PDCCH region. Similarly to the L-PDCCH, the E-PDCCHcarries DCI. For example, the E-PDCCH may carry downlink schedulinginformation and uplink scheduling information. For example, the UE mayreceive the E-PDCCH and receive data/control information via a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information via a PUSCH correspondingto the E-PDCCH. The E-PDCCH/PDSCH may be allocated starting from a firstOFDM symbol of the subframe, according to cell type. In thisspecification, the PDCCH includes both L-PDCCH and EPDCCH unlessotherwise noted.

FIG. 6 illustrates an uplink subframe structure.

Referring to FIG. 6, an uplink subframe includes a plurality of (e.g. 2)slots. A slot may include different numbers of SC-FDMA symbols accordingto CP lengths. For example, a slot may include 7 SC-FDMA symbols in anormal CP case. The uplink subframe is divided into a control region anda data region in the frequency domain. The data region is allocated witha PUSCH and used to carry a data signal such as audio data. The controlregion is allocated a PUCCH and used to carry control information. ThePUCCH includes an RB pair (e.g. m=0, 1, 2, 3) located at both ends ofthe data region in the frequency domain and hopped in a slot boundary.Control information includes HARQ ACK/NACK, CQI, PMI, RI, etc.

FIG. 7 illustrates carrier aggregation (CA) communication system.

Referring to FIG. 7, a plurality of UL/DL component carriers (CCs) canbe aggregated to support a wider UL/DL bandwidth. The CCs may becontiguous or non-contiguous in the frequency domain. Bandwidths of theCCs can be independently determined. Asymmetrical CA in which the numberof UL CCs is different from the number of DL CCs can be implemented.Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC and other CCsmay be referred to as secondary CCs. For example, when cross-carrierscheduling (or cross-CC scheduling) is applied, a PDCCH for downlinkallocation can be transmitted on DL CC #0 and a PDSCH correspondingthereto can be transmitted on DL CC #2. The term “component carrier” maybe replaced by other equivalent terms (e.g. “carrier”, “cell”, etc.).

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.    -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have CIF

CIF corresponds to a fixed x-bit field (e.g. x=3) (when CIF is set)

CIF position is fixed irrespective of DIC format size (when CIF is set)

When the CIF is present, the BS may allocate a monitoring DL CC (set) toreduce BD complexity of the UE. For PDSCH/PUSCH scheduling, the UE maydetect/decode a PDCCH only on the corresponding DL CCs. The BS maytransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set may be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 8 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A˜C may be referred to as a serving CC, servingcarrier, serving cell, etc. When the CIF is disabled, each DL CC cantransmit only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF according to LTE PDCCH rule (non-cross-CC scheduling).When the CIF is enabled through UE-specific (or UE-group-specific orcell-specific) higher layer signaling, a specific CC (e.g. DL CC A) cantransmit not only the PDCCH that schedules the PDSCH of DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF(cross-scheduling). A PDCCH is not transmitted on DL CC B and DL CC C.

Embodiment: Signal Transmission and Reception in LTE-U

As more and more telecommunication devices require greater communicationcapacity, efficient utilization of limited frequency bands in futurewireless communication systems is increasingly important. Basically, thefrequency spectrum is divided into a licensed band and an unlicensedband. The licensed band includes frequency bands reserved for specificuses. For example, the licensed band includes government allocatedfrequency bands for cellular communication (e.g., LTE frequency bands).The unlicensed band is a frequency band reserved for public use and isalso referred to as a license-free band. The unlicensed band may be usedby anyone without permission or declaration so long as such use meetsradio regulations. The unlicensed band is distributed or designated foruse by anyone at a close distance, such as within a specific area orbuilding, in an output range that does not interfere with thecommunication of other wireless stations, and is widely used forwireless remote control, wireless power transmission, Wi-Fi, and thelike.

Cellular communication systems such as LTE systems are also exploringways to utilize unlicensed bands (e.g., the 2.4 GHz band and the 5 GHzband), used in legacy Wi-Fi systems, for traffic off-loading. Basically,since it is assumed that wireless transmission and reception isperformed through contention between communication nodes, it is requiredthat each communication node perform channel sensing (CS) beforetransmitting a signal and confirm that none of the other communicationnodes transmit a signal. This operation is referred to as clear channelassessment (CCA), and an eNB or a UE of the LTE system may also need toperform CCA for signal transmission in an unlicensed band. Forsimplicity, the unlicensed band used in the LTE-A system is referred toas the LTE-U band. In addition, when an eNB or UE of the LTE systemtransmits a signal, other communication nodes such as Wi-Fi should alsoperform CCA in order not to cause interference. For example, in the801.11ac Wi-Fi standard, the CCA threshold is specified to be −62 dBmfor non-Wi-Fi signals and −82 dBm for Wi-Fi signals. Accordingly, thestation (STA)/access point (AP) does not perform signal transmission soas not to cause interference when a signal other than Wi-Fi signals arereceived at a power greater than or equal to −62 dBm. In a Wi-Fi system,the STA or AP may perform CCA and signal transmission if a signal abovea CCA threshold is not detected for more than 4 μs.

FIG. 9 illustrates CA of a licensed band and an unlicensed band.Referring to FIG. 9, an eNB may transmit a signal to a UE or the UE maytransmit a signal to the eNB, in a CA situation of the licensed band(hereinafter, LTE-A band or L-band) and the unlicensed band(hereinafter, LTE-U band or U-band). Herein, a cell (e.g., a PCell or anSCell) operating on the L-band is defined as an LCell and a carrier ofthe LCell is defined as a (DL/UL) LCC. In addition, a cell (e.g., anSCell) operating on the U-band is defined as a UCell and a carrier ofthe UCell is defined as a (DL/UL) UCC. A carrier/carrier-frequency of acell may represent an operation frequency (e.g., a center frequency). Acell/carrier (e.g., CC) is referred to as a cell.

FIGS. 10 and 11 illustrate a resource reservation method on an LTE-Uband. In order to perform communication on the LTE-U band, the eNB andthe UE are able to occupy/secure the LTE-U band for a specific timeduration through contention with other communication systems (e.g.,Wi-Fi) irrelevant to an LTE-A system. For convenience, the time durationoccupied/secured for cellular communication on the LTE-U band isreferred to as a reserved resource period (RRP). The RRP may representdiscontinuously/aperiodically configured resources depending on acarrier sensing result. To secure the RRP, various methods may be used.For example, a specific reservation signal may be transmitted in the RRPso that other communication system devices such as Wi-Fi may recognizethat a radio channel is busy. As an example, the eNB may continuouslytransmit an RS and a data signal in the RRP so that a signal of aspecific power level or more may be seamlessly transmitted during theRRP. If the eNB has determined, in advance, the RRP that the eNB desiresto occupy on the LTE-U band, the eNB may pre-indicate the RRP to the UEso that the UE may maintain a communication transmission/reception linkduring the indicated RRP. As a scheme of indicating information aboutthe RRP to the UE, the eNB may transmit the information about the RRPthrough another CC (e.g., the LTE-A band) connected in the form of CA.

For example, the RRP including M consecutive subframes (SFs) may beconfigured. Unlike this, one RRP may be configured by an SF set in whichSFs are discontinuously present (not shown). In addition, the RRP may beconfigured only by DL SFs (and/or (?? or) UL SFs) or by a combination ofDL SFs and UL SFs, according to a traffic situation. For convenience ofdescription, the RRP configured only by DL (UL) SFs is referred to as aDL (UL) only RRP and the RRP configured by a combination of DL SFs andUL SFs is referred to as a DL/UL mixed RRP. The DL/UL mixed RRP may havea structure including only (single) DL-to-UL switching or a structureincluding only (single) UL-to-DL switching. Herein, the eNB maypre-inform the UE of RRP configuration information (e.g., the value of Mand the usage of M SFs) through higher layer (e.g., RRC or MAC)signaling (using a PCell) or through a physical control/data channel.The start point of the RRP may be periodically set by higher layer(e.g., RRC or MAC) signaling. In addition, if it is desired that thestart point of the RRP be set to SF #n, the start point of the RRP maybe designated through physical layer signaling (e.g., (E)PDCCH) in SF #nor SF#(n−k) wherein k is a positive integer (e.g., 4).

The RRP may be configured such that an SF boundary or SF number/indexconfigured on an SCell is aligned with that configured on a PCell(hereinafter, aligned-RRP) (see FIG. 10) or the SF boundary or SFnumber/index configured on the SCell is misaligned with that configuredon the PCell (hereinafter, floating-RRP) (see FIG. 11). In the presentinvention, that SF boundaries between cells are aligned may indicatethat an interval between SF boundaries of two different cells is lessthan a specific time (e.g., CP length or X μs (X≧0)). In addition, inthe present invention, the PCell may mean a cell which is referenced todetermine the SF (and/or symbol) boundary of a UCell in terms of time(and/or frequency) synchronization.

As another operation example on the LTE-U band operating according to acontention based random access scheme, the eNB may first perform carriersensing prior to data transmission and reception. The eNB may checkwhether a current channel state of the SCell is busy or idle and, uponchecking that the current channel state of the SCell is idle, the eNBmay transmit a scheduling grant (e.g., (E)PDCCH) through the L-band (orPCell) or the U-band (or SCell) and attempt to perform data transmissionand reception on the UCell. For convenience, scheduling of the UCellfrom the same cell is referred to as self-CC scheduling and schedulingof the UCell from another cell (e.g., PCell) is referred to as cross-CCscheduling.

As described above, since an LTE-U system operating based on carriersensing on the LTE-U band has a structure in which an available resourceduration is aperiodically or discontinuously secured/configured, datascheduling/transmission through the LTE-U band has a possibility ofbeing opportunistically/intermittently performed depending only on sucha temporarily configured resource duration.

Meanwhile, a situation in which a plurality of UCells operates on theU-band may be considered. In addition, a situation in which an RRPstructure (e.g., an RRP start point, an RRP length, an SF configurationin the RRP, etc.) is dynamically/flexibly changed/configured on eachUCell according to traffic requirements of the UE may be considered. Inthis case, UL-to-DL and/or DL-to-UL interference may occur between RRPsof plural UCells that are contiguous or relatively near in frequency(because the RRP start point, RRP length, and SF configuration differ).In this case, inter-cell UL-DL interference may be UE-specifically orUE-commonly generated according to situation. Therefore, inconsideration of inter-cell UL-DL interference, a method of stablyestablishing RRP durations/configurations of plural UCells oreffectively controlling an influence of inter-UCell interference isneeded.

Hereinafter, a CA method and a resource allocation/configuration methodof effectively securing an available resource duration in a situation inwhich a plurality of cells/carriers is configured are proposed. Herein,the plural cells include one or more cells operating on an L-band andone or more cells on which an available resource duration isaperiodically or discontinuously secured/configured. The presentinvention may be applied to an LTE-U system opportunistically operatingon the U-band based on carrier sensing. The present invention may alsobe applied to a situation in which an LTE-U scheme is configured in aplurality of cells. Specifically, the present invention proposes CA of aplurality of UCells, a control method therefor, and an RRP configurationmethod suitable for the UCells, in a situation in which an RRP isdynamically/flexibly set/configured.

For convenience, it will be assumed hereinbelow that one L-band and oneU-band are carrier-aggregated for a UE and wireless communication isperformed through the carrier-aggregated bands. For example, a CAsituation between a PCell operating on a legacy L-band and an SCelloperating according to the LTE-U scheme is considered. However, theproposed methods of the present invention may be applied to a situationin which a plurality of L-bands and a plurality of U-bands arecarrier-aggregated. In addition, the present invention may be appliedeven to the case in which data transmission/reception is performedbetween the eNB and the UE only on the U-band. The proposed methods ofthe present invention may be extended not only to a 3GPP LTE system butalso to systems having other characteristics. Hereinbelow, the eNB willbe used as an extensive term including remote radio head (RRH), basestation (BS), transmission point (TP), reception point (RP), relay, etc.

(1) CA Between Multiple UCells and Control Method Therefor

To solve inter-cell UL-DL interference when an RRP isdynamically/flexibly changed/configured on each UCell, a method ofconfiguring a UCell group in which SF directions (on the RRP) areconfigured to be the same at the same timing is proposed. Moregenerally, a method of configuring a cell group including a legacy LCelldeployed on an L-band, in which SF directions are configured to be thesame at the same timing is proposed. The cell group may include onlyUCells or include both UCells and LCells. In addition, in considerationof transmission/reception (switching) operation complexity of a UE, aUCell group using/configuring the same RRP type (e.g., one of two (orthree) types of a DL (UL) only RRP and a DL/UL mixed RRP or one of three(or four) types of a DL (UL) only RRP, a DL-to-UL RRP, and a UL-to-DLRRP) or the same RRP type set may be configured. Accordingly, in thefollowing description, an SF direction may be replaced with an RRP type.

As one method, in a cell group including only UCells, SFs on UCells maybe configured to be aligned with an SF direction of a specific UCell(hereinafter, a reference UCell). The reference UCell may be designatedby an eNB when a cell group is designated/configured. In this case, theeNB may signal RRP configuration information about the reference UCellto a UE. Then, the UE may perform a signal transmission/receptionoperation under the assumption that an RRP is configured to be the sameas the reference UCell even in other UCells in the cell group (or thatan RRP having the same SF direction as the reference UCell may beconfigured even on other UCells at an RRP configuration timing on thereference UCell). In addition, in a cell group including both LCells andUCells, SF directions of the UCells may be configured to be aligned withSF directions of the LCell. As another method, if a UCell group isconfigured, SF directions (at the same timing) are configured to be thesame on all UCells in the group or the same RRP type may beused/configured. In this case, if an RRP for any one UCell in the cellgroup is configured, the UE may perform a signal transmission/receptionoperation under the assumption that an RRP is identically configuredwith respect to the other UCells in the cell group (or that an RRPhaving the same SF direction as any one UCell may be configured withrespect to the other UCells at an RRP configuration timing of thecorresponding UCell). As another method, to simplify atransmission/reception (switching) operation of the UE, (withoutadditionally designating a UCell group based on the same SF direction orthe same RRP type) SF directions (and/or RRP types) on all UCellscarrier-aggregated for one UE may be identically configured or SFdirections at the same timing on all UCells carrier-aggregated for oneUE may be identically configured.

Meanwhile, as another method for solving inter-cell interference, if SFdirections (on an RRP) of a plurality of specific UCells (or a pluralityof predesignated UCells regardless of the UCell group) in a UCell groupare differently configured at the same timing, the UE may operate asfollows.

Alt 1) The UE may perform a signal (e.g., PDSCH or PUSCH)transmission/reception operation only on UCells in which SFs alignedwith a (predesignated) specific SF direction (e.g., DL or UL) or an SFdirection configured for a specific UCell (hereinafter, a referenceUCell) (an LCell when a cell group including the LCell is considered)are configured among a plurality of UCells. Accordingly, the UE mayomit/drop signal transmission/reception on a UCell in which an SF havingan SF direction different from an SF direction configured on thereference UCell (or LCell) is configured, even though signal (e.g.,PDSCH or PUSCH) transmission/reception is scheduled on the correspondingcell. As signal transmission is omitted/dropped, a carrier sensingprocedure performed to identify whether a radio channel state (i.e.,idle or busy) prior to signal transmission may be omitted/skipped. In acell group including only UCells, the reference UCell may be designatedby the eNB. If the LCell is a TDD cell, an SF direction of the LCell maybe determined according to a UL-DL configuration of Table 1.

Alt 2) An independent DL CSI measurement/reporting and/or UL powercontrol process may be applied to an SF direction collision timing(hereinafter, a collided SF) (between UCells) separately from an SFdirection aligned timing (hereinafter, an aligned SF) (withoutadditional restriction on a transmission/reception operation).

In Alt 2, when the UE performs DL CSI measurement/reporting, anindependent periodic CSI process (e.g., a CSI content type or areporting timing/period) may be applied to the aligned SF and thecollided SF. In addition, when a (PUSCH based) aperiodic CSI request isperformed, whether a CSI measurement target SF is the aligned SF or thecollided SF may be indicated through corresponding UL grant DCI. In Alt2, when a UL power control (PC) process is performed, independentopen-loop PC parameters (e.g., P_(O) _(_) _(PUSCH,c)(j)) may beconfigured for the aligned SF and the collided SF. P_(O) _(_)_(PUSCH,c)(j) denotes a parameter/offset value used for power controlfor PUSCH transmission in SF #j of cell #c. In addition, TPC commands(e.g., δPUSCH,c) may be separately accumulated with respect to thealigned SF and the collided SF (i.e., only in SFs of the same type).

Meanwhile, in terms of SF directions and SF collision, a DL SF (UCell)in the present invention may include not only a time duration duringwhich the eNB transmits/can transmit a signal for the purpose of datascheduling/transmission but also a time duration during which the eNBtransmits/can transmit a specific signal (hereinafter, a reservationsignal) for the purpose of radio channel reservation on the UCell. Inaddition, a UL SF (UCell) in the present invention may include not onlya time duration during which the UE transmits/can transmit data/controlinformation but also a time duration during which the UE transmits/cantransmit the reservation signal on the UCell. From the same perspective,an SF (e.g., a TDD special SF) of a type in which a DL transmissionsymbol/duration and a UL transmission symbol/duration coexist may beincluded 1) both in the DL SF and in the UL SF or 2) in the DL SF whenonly DL data scheduling is configured to be performed in thecorresponding SF and in the UL SF when only UL data scheduling isconfigured to be performed in the corresponding SF.

(2) DL/UL Mixed RRP Configuration Scheme on UCell

In this example, a DL/UL mixed RRP configuration scheme considering ULself-CC scheduling on a UCell is proposed. Herein, UL self-CC schedulingmeans a structure in which UL grant DCI for scheduling PUSCHtransmission on the UCell and a PHICH corresponding to a PUSCH aretransmitted on the UCell. Specifically, assuming that a time delayconsumed for a UL grant/PHICH-to-PUSCH and a PUSCH-to-PHICH/UL grant fora DL-to-UL RRP and a UL-to-DL RRP, respectively, is 4 SFs (or, 4 ms),the following SF configurations (e.g., RRP configurations) may beconsidered. For convenience, DL and UL are referred to as D and U,respectively.

In this example, an SF configuration (e.g., RRP configuration) may bepre-shared between the eNB and the UE. As an example, uponadding/configuring a UCell for the UE, the eNB may inform the UE ofinformation about an RRP pattern applied to the UCell (e.g., an RRPpattern index) through higher layer signaling (e.g., RRC signaling orLayer 2 (L2)) and then, upon transmitting a UL/DL grant PDCCH, include,in the UL/DL grant PDCCH, information about in which place on an RRP aDL SF in which the UL/DL grant PDCCH is transmitted is located. Asanother example, a method may be considered in which a bitmapcorresponding to an RRP SF pattern is included in the UL/DL grant PDCCH,a bit value corresponding to a DL SF in which the UL/DL grant PDCCH istransmitted is set to 1 and the other bit value of the bitmap is set to0.

<DL-to-UL RRP>

Case 1) Four (or Four or More) DL SFs+Four or Fewer UL SFs

(e.g., DDDDU or DDDDUU or DDDDUUU or DDDDUUUU)

A PUSCH of a UL SF (e.g., SF #n) may be scheduled by a PHICH/UL granttransmitted/received through a DL SF configured in SF #(n−4). NoPHICH/UL grant is transmitted/received and/or only a DL grant may betransmitted/received through the other DL SFs. Accordingly, the UE mayperform a reception processing process (e.g., decoding) of a controlchannel under the assumption that the PHICH/UL grant/DL grant can betransmitted/received in a DL SF with a corresponding UL SF in an RRP. Onthe other hand, the UE may perform a reception processing process (e.g.,monitoring or decoding) of a control channel under the assumption thatno PHICH/UL grant is transmitted/received and/or only the DL grant maybe transmitted/received in a DL SF without a corresponding UL SF in theRRP. For example, the UE may omit/drop the reception processing process(e.g., monitoring or decoding) of the PHICH/UL grant. In addition, evenwhen the PHICH/UL grant is detected, the UE may omit/drop a PUSCHtransmission process according to detection of the PHICH/UL grant.

<UL-to-DL RRP>

Case 2) Four or Fewer UL SFs+Four (or Four or More) DL SFs

(e.g., UDDDD or UUDDDD or UUUDDDD or UUUUDDDD)

A PHICH/UL grant corresponding to a PUSCH of a UL SF (e.g., SF #n) maybe transmitted/received by a DL SF configured in SF #(n−4). No PHICH/ULgrant is transmitted/received and/or only a DL grant may betransmitted/received through the other DL SFs. Accordingly, the UE mayperform a reception processing process (e.g., decoding) of a controlchannel under the assumption that the PHICH/UL grant/DL grant can betransmitted/received in a DL SF with a corresponding UL SF in an RRP. Onthe other hand, the UE may perform a reception processing process (e.g.,monitoring or decoding) of a control channel under the assumption thatno PHICH/UL grant is transmitted/received and/or only the DL grant maybe transmitted/received in a DL SF without a corresponding UL SF in theRRP. For example, the UE may omit/drop the reception processing process(e.g., monitoring or decoding) of the PHICH/UL grant. In addition, evenwhen the PHICH/UL grant is detected, the UE may omit/drop a PUSCHtransmission process according to detection of the PHICH/UL grant.

More generally, assuming that a time delay consumed for a ULgrant/PHICH-to-PUSCH is K1 SFs (or K1 ms) and a time delay consumed fora PUSCH-to-PHICH/UL grant is K2 SFs (or K2 ms), the following SFconfigurations may be considered.

<DL-to-UL RRP>

Case 1) K1 (or K1 or More) DL SFs+K1 or Fewer UL SFs

A PUSCH of a UL SF (e.g., SF #n) may be scheduled by a UL grant/PHICHtransmitted/received through a DL SF configured in SF #(n−K1). The ULgrant/PHICH may not be transmitted/received and/or only a DL grant maybe transmitted/received through the other DL SFs.

<UL-to-DL RRP>

Case 2) K2 or Fewer UL SFs+K2 (or K2 or More) DL SFs

A PHICH/UL grant corresponding to a PUSCH of a UL SF (e.g., SF #n) maybe transmitted/received through a DL SF configured in SF #(n+K2). ThePHICH/UL grant may not be transmitted/received and/or only a DL grantmay be transmitted/received through the other DL SFs.

(3) Carrier Sensing Method Based on LTE-U Signal Detection

Upon considering a situation in which a device (e.g., eNB or UE)performing transmission of a specific signal/channel through a UCell inan LTE-U system performs a carrier sensing operation, the eNB and the UEmay be requested to perform carrier sensing for a radio channel of theUCell prior to DL signal/channel transmission and UL signal/channeltransmission, respectively. In this case, in a situation in which aspecific SF configuration (e.g., RRP type) is considered, it may beeffective to perform carrier sensing based on LTE-U signal detection(rather than simple energy/power level detection), for contiguous UCellradio channel reservation/occupation of the LTE-U system. Herein, LTE-Usignal detection means detection of a signal transmitted by anotherLTE-U device (e.g., eNB or UE). The LTE-U signal indicates a wirelesssignal transmitted on the UCell based on 3GPP LTE specifications andLTE-U device indicates an LTE device (e.g., eNB or UE) supporting signaltransmission/reception on the UCell. In relation to the LTE-U signaldetection based carrier sensing operation, the following three cases maybe considered.

Case A) UE Performing Signal/Channel Transmission Through UL SF #(n+1)Immediately after UL SF #n

When signal/channel (e.g., PUSCH, PUCCH, or PRACH) transmissionreserved/scheduled on a UCell is present in UL SF #(n+1), the UE mayperform an operation of detecting an LTE-U signal transmitted by anotherUE in UL SF #n on the UCell. The UE may determine, through comparisonbetween the detection result (e.g., a correlation value) and a specificthreshold value, whether another LTE-U device (e.g., an LTE-U UE)occupies a radio channel of the UCell in UL SF #n. As the comparisonresult, if it is determined that another LTE-U device occupies the radiochannel of the UCell in UL SF #n, the UE may determine that the state ofthe radio channel of the UCell in UL SF #(n+1) is idle and performsignal/channel (e.g., PUSCH, PUCCH, or PRACH) transmissionreserved/scheduled on the UCell in UL SF #(n+1). Meanwhile, if it isdetermined that a non-LTE-U device occupies the radio channel of theUCell in UL SF #n, the UE may determine that the state of the radiochannel of the UCell in UL SF #(n+1) is busy and drop/omitsignal/channel transmission reserved/scheduled on the UCell in UL SF#(n+1).

The LTE-U signal, which is a detection target, may be a (PUSCH) DMRSsignal or an SRS signal. For more efficient detection, the eNB maypre-signal LTE-U signal transmission related information/parameters tothe UE. For example, the LTE-U signal transmission relatedinformation/parameters include sequence information constituting theLTE-U signal (e.g., a base sequence or a cyclic shift), a frequencyresource on which the LTE-U signal is transmitted (or on which the LTE-Usignal is to be detected), a time resource on which the LTE-U signal istransmitted (or on which the LTE-U signal is to be detected) (e.g., anSC-FDMA symbol index), and the specific threshold value used todetermine the detection result. The LTE-U signal transmission relatedinformation/parameters may be cell-commonly or UE-group-commonlyconfigured.

Meanwhile, a UE performing only SRS signal transmission through the lastsymbol in UL SF #n (or arbitrary UL SF #n without limiting to Case A)may also perform a carrier sensing operation based on the LTE-U signal(in SF #n) similarly to the above example. In addition, even when the UEoperates to perform UL signal/channel (e.g., PUSCH, PUCCH, or PRACH)transmission through symbols except for the first partial symbols in ULSF #n (or arbitrary UL SF #n without limiting to Case A), the UE mayperform the carrier sensing operation based on LTE-U signal detection(on first partial symbols of SF #n) similar to the above example.

Case B) UE Performing Signal/Channel Transmission Through UL SF #(n+1)Immediately after DL SF #n

When signal/channel (e.g., PUSCH, PUCCH, or PRACH) transmissionreserved/scheduled on a UCell is present in UL SF #(n+1), the UE mayperform an operation of detecting an LTE-U signal transmitted by the eNBin UL SF #n on the UCell. The UE may determine, through comparisonbetween the detection result (e.g., a correlation value) and a specificthreshold value, whether an LTE-U device (e.g., an LTE-U eNB) occupies aradio channel of the UCell. As the comparison result, if it isdetermined that another LTE-U device occupies the radio channel of theUCell in UL SF #n, the UE may determine that the state of the radiochannel of the UCell in UL SF #(n+1) is idle and perform signal/channel(e.g., PUSCH, PUCCH, or PRACH) transmission reserved/scheduled on theUCell in UL SF #(n+1). Meanwhile, if it is determined that a non-LTE-Udevice occupies the radio channel of the UCell in UL SF #n, the UE maydetermine that the state of the radio channel of the UCell in UL SF#(n+1) is busy and drop/omit signal/channel transmissionreserved/scheduled on the UCell in UL SF #(n+1).

The LTE-U signal, which is a detection target, may be a specific RS(e.g., a discovery RS, a CSI-RS, or a CRS) or a synchronization signal(e.g., a PSS/SSS or a known reservation signal). For more efficientdetection, the eNB may pre-signal LTE-U signal transmission relatedinformation/parameters to the UE. For example, the LTE-U signaltransmission related information/parameters include sequence informationconstituting the LTE-U signal, a frequency shift of the LTE-U signal, afrequency resource on which the LTE-U signal is transmitted (or on whichthe LTE-U signal is to be detected), a time resource on which the LTE-Usignal is transmitted (or on which the LTE-U signal is to be detected)(e.g., an OFDMA symbol index), and the specific threshold value used todetermine the detection result. The LTE-U signal transmission relatedinformation/parameters may be cell-commonly or UE-group-commonlyconfigured.

Meanwhile, when DL SF #n has a special SF structure, a UE performingonly specific UL signal/channel (e.g., SRS or a PRACH) transmissionthrough the last partial symbols in DL SF #n may also perform thecarrier sensing operation based on LTE-U signal detection (in SF #n)similar to the above example.

Case C) eNB Performing Signal/Channel Transmission Through DL SF #(n+1)Immediately after UL SF #n

When a signal/channel (e.g., an (E-)PDCCH, PHICH, or PDSCH) to betransmitted is present on a UCell in DL SF #(n+1), the eNB may performan operation of detecting an LTE-U signal transmitted by the UE in UL SF#n on the UCell. The eNB may determine, through comparison between thedetection result (e.g., a correlation value) and a specific thresholdvalue, whether an LTE-U device (e.g., an LTE-U UE) occupies a radiochannel of the UCell. As the comparison result, if it is determined thatanother LTE-U device occupies the radio channel of the UCell in UL SF#n, the eNB may determine that the state of the radio channel of theUCell in DL SF #(n+1) is idle and perform signal/channel transmission onthe UCell in DL SF #(n+1). Meanwhile, if it is determined that anon-LTE-U device occupies the radio channel of the UCell in UL SF #n,the eNB may determine that the state of the radio channel of the UCellin DL SF #(n+1) is busy and drop/omit signal/channel transmission on theUCell in DL SF #(n+1). The LTE-U signal, which is a detection target,may be the (PUSCH) DMRS signal or the SRS signal as in Case A.

Meanwhile, upon succeeding in detection of the LTE-U signal throughcarrier sensing (e.g., when a detection value exceeds the specificthreshold value), the LTE-U device (e.g., the UE in Case A/B and the eNBin Case C) performing carrier sensing may perform the followingoperations.

Alt 1: The LTE-U device may eliminate (or disregard) the LTE-U signaldetected in SF #n from a received signal, perform normal energy (orpower) detection based carrier sensing on the remaining signal, andfinally determine a radio channel state (e.g., idle or busy) of theUCell in SF #(n+1) (or SF #n) according to the carrier sensing result.

Alt 2: Upon succeeding in detection of the LTE-U signal in SF #n, theLTE-U device may determine (without an additional operation) that theradio channel state of the UCell in SF #(n+1) (or SF #n) is idle andthen perform a signal transmission operation (e.g., signal/channeltransmission reserved/scheduled on the UCell) on the UCell in SF #(n+1)(or SF #n).

On the other hand, upon failing to detect the LTE-U signal in SF #n(e.g., if the detection value is less than the specific thresholdvalue), the LTE-U device may perform normal energy (or power) detectionbased carrier sensing on a received signal in SF #n and finallydetermine a radio channel state (e.g., idle or busy) of the UCell in SF#(n+1) (or SF #n) according to the carrier sensing result. If it isdetermined that the radio channel state of the UCell in SF #(n+1) (or SF#n) is idle, the LTE-U device may perform a signal transmissionoperation (e.g., signal/channel transmission reserved/scheduled on theUCell) on the UCell in SF #(n+1). If it is determined that the radiochannel state of the UCell in SF #(n+1) (or SF #n) is busy, the LTE-Udevice may drop/omit a signal transmission operation on the UCell in SF#(n+1).

In addition, the LTE-U signal detection based carrier sensing operationmay be performed as follows according to implementation of theoperation.

Step 1: The LTE-U device may perform normal energy (or power) detectionbased carrier sensing with respect to a received signal of a UCell in SF#n. If it is determined that the radio channel state of the UCell in SF#(n+1) (or SF #n) is idle as a result of carrier sensing (e.g.,comparison between a signal detection result and a specific thresholdvalue), the LTE-U device may perform signal transmission operation(e.g., signal/channel transmission reserved/scheduled on the UCell) onthe UCell of SF #(n+1) (or SF #n) and, if it is determined that theradio channel state is busy, the LTE-U device may perform Step 2described below.

Step 2: The LTE-U device may perform an LTE-U signal detection operationwith respect to the received signal of the UCell in SF #n. Uponsucceeding in detecting the LTE-U signal (through comparison between thesignal detection result and the specific threshold value), the LTE-Udevice may determine that the radio channel state of the UCell is idlein SF #(n+1) (or SF #n). If it is determined that the radio channelstate of the UCell in SF #(n+1) (or SF #n) is idle, the LTE-U device mayperform a signal transmission operation (e.g., signal/channeltransmission reserved/scheduled on the UCell) on the UCell in SF #(n+1)(or SF #n). Meanwhile, if it is determined that the radio channel stateof the UCell in SF #(n+1) (or SF #n) is busy, the LTE-U device maydrop/omit the signal transmission operation on the UCell in SF #(n+1)(or SF #n).

While the proposed methods of the present invention have been separatelydescribed for convenience, the methods may be used in combination. Forexample, when an RRP is configured on a UCell in a cell group, the RRPmay be configured by the DL/UL mixed RRP configuration scheme proposedin the present invention and signal transmission in the RRP may beperformed in a signal transmission process depending on LTE-U signaldetection based carrier sensing.

FIG. 12 illustrates a communication procedure according to an embodimentof the present invention. The present invention may be applied to a 3GPP(3rd Generation Partnership Project) wireless communication system. Adescription will be given based on a UE for convenience but anassociated operation may be performed by an eNB.

Referring to FIG. 12, the UE may configure a cell group including aplurality of UCells (S1202). The UE may identify SF configurationinformation about a specific cell of the cell group (S1204). Next, theUE may configure SF transmission directions of cells in the cell groupto be the same at the same timing, based on the SF configurationinformation about the specific cell (S1206). Herein, when the cell groupincludes only UCells, the specific cell may be any one of the UCells inthe cell group. The specific UCell may be designated by the eNB upondesignating/allocating the cell group. Meanwhile, when the cell groupincludes an LCell, the specific cell may be the LCell.

Herein, configuring SF transmission directions of cells in the cellgroup to be the same at the same timing may include configuring RRPs onthe UCells in the cell group to be the same and an RRP may indicate aresource temporarily configured on each UCell. In addition, the RRP mayinclude a plurality of contiguous DL SFs and a plurality of contiguousUL SFs subsequent to the DL SFs. Specifically, the RRP may include K1contiguous DL SFs and subsequent K1 or fewer contiguous UL SFs. In thiscase, if signal transmission is scheduled in an (n+1)-th SF in the RRP,a signal transmission process is performed according to a carriersensing result in an n-th SF, wherein, if a signal (e.g., an LTE-Usignal) related to a parameter indicated by the eNB in the n-th SF isdetected, the UE performs signal transmission in the (n+1)-th SF, and nosignal related to the parameter indicated by the eNB is detected in then-th SF, whether signal transmission is performed in the (n+1)-th SF maybe determined according to an energy level in the n-th SF.

The CA method of the present invention may not be limitedly applied onlyto a cell operating based on an aperiodic RRP configuration such asLTE-U but may be similarly applied to a normal cell operating based on atransmission resource configuration such as in legacy LTE.

FIG. 13 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present invention.

Referring to FIG. 13, the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE can be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present invention. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention mentioned in the foregoingdescription may be applicable to a user equipment, a base station, orother devices of wireless mobile communication systems.

What is claimed is:
 1. A method of performing communication by a userequipment (UE) in a wireless communication system, the methodcomprising: configuring a cell group including a plurality of unlicensedband cells (UCells); identifying subframe configuration informationabout a specific cell in the cell group; and configuring subframetransmission directions of cells in the cell group to be the same at thesame timing, based on the subframe configuration information about thespecific cell, wherein, if the cell group includes only the UCells, thespecific cell is any one of the UCells in the cell group, and if thecell group includes a licensed band cell (LCell), the specific cell isthe LCell.
 2. The method according to claim 1, wherein configuringsubframe transmission directions of cells in the cell group to be sameat the same timing includes configuring reserved resource periods (RRPs)on the UCells in the cell group to be the same and each of the RRPsindicates a resource temporarily configured on each UCell.
 3. The methodaccording to claim 2, wherein the RRP includes a plurality of contiguousdownlink (DL) subframes and a plurality of contiguous uplink (UL)subframes subsequent to the DL subframes.
 4. The method according toclaim 3, wherein the RRP includes K1 contiguous DL subframes and K1 orfewer contiguous UL subframes subsequent to the K1 contiguous DLsubframes.
 5. The method according to claim 3, further comprisingperforming a signal transmission process according to a carrier sensingresult in an n-th subframe when signal transmission is scheduled in an(n+1)-th subframe in the RRP, wherein, if a signal related to aparameter indicated by a base station (BS) is detected in the n-thsubframe, signal transmission is performed in the (n+1)-th subframe, andif no signal related to the parameter indicated by the eNB is detectedin the n-th subframe, whether signal transmission is performed in the(n+1)-th subframe is determined according to an energy level in the n-thsubframe.
 6. The method according to claim 1, wherein the wirelesscommunication system is a 3rd generation partnership project (3GPP)wireless communication system.
 7. A user equipment (UE) for performingcommunication in a wireless communication system, the UE comprising: aradio frequency (RF) module; and a processor, wherein the processor isconfigured to configure a cell group including a plurality of unlicensedband cells (UCells), identify subframe configuration information about aspecific cell in the cell group, and configure subframe transmissiondirections of cells in the cell group to be the same at the same timing,based on the subframe configuration information about the specific cell,and wherein, if the cell group includes only the UCells, the specificcell is any one of the UCells in the cell group, and if the cell groupincludes a licensed band cell (LCell), the specific cell is the LCell.8. The UE according to claim 7, wherein configuring subframetransmission directions of cells in the cell group to be same at thesame timing includes configuring reserved resource periods (RRPs) on theUCells in the cell group to be the same and each of the RRPs indicates aresource temporarily configured on each UCell.
 9. The UE according toclaim 8, wherein the RRP includes a plurality of contiguous downlink(DL) subframes and a plurality of contiguous uplink (UL) subframessubsequent to the DL subframes.
 10. The UE according to claim 9, whereinthe RRP includes K1 contiguous DL subframes and K1 or fewer contiguousUL subframes subsequent to the K1 contiguous DL subframes.
 11. The UEaccording to claim 9, wherein, if signal transmission is scheduled in an(n+1)-th subframe in the RRP, a signal transmission process is performedaccording to a carrier sensing result in an n-th subframe, if a signalrelated to a parameter indicated by a base station (BS) is detected inthe n-th subframe, signal transmission is performed in the (n+1)-thsubframe, and if no signal related to the parameter indicated by the eNBis detected in the n-th subframe, whether signal transmission isperformed in the (n+1)-th subframe is determined according to an energylevel in the n-th subframe.
 12. The UE according to claim 7, wherein thewireless communication system is a 3rd generation partnership project(3GPP) wireless communication system.